1. Field of the Invention
The present invention relates generally to recording apparatus for recording an image on a recording medium and, more particularly, to a recording apparatus arranged to allow an operator to freely erase an image that has been erroneously recorded on the recording medium.
The term "recording apparatus" used herein embraces electronic typewriters, printers, word processors, copying machines and so forth. The term "image" used herein embraces alphanumerical characters, symbols, and graphic patterns. The term "recording medium" used herein embraces ordinary paper, typing paper, plastic sheets for use with an OHP, and so forth.
2. Related Background Art
In a conventional type of typewriter with a erasure function, in printing, an inked ribbon is shifted to a print position at which the inked ribbon is struck through a desired character to thereby effect printing. Each time one character is printed, a carriage which carries a print head or the inked ribbon is moved at a pitch equivalent to one character. In this print operation, if a character is erroneously printed, the same character as the erroneously printed character is selected and an erasure tape is shifted to the print position. Then, an erasure impact is applied to the surface of the printing paper through the selected character to peel off the ink of the wrong character recorded on the surface of the printing paper. This erasure tape is divided into two major types: one is of a so-called lift-off type that has an adhesive portion which peels off the ink of a wrong character by its adhesive force and the other is of a so-called cover-up type that erases the ink of a wrong character by covering it with white ink.
In an erasure operation, it is difficult to make the position of a printed character coincide with a position at which a character is to be printed for erasure purposes. For this reason, a small unerased portion may be left because of this dislocation. In order to eliminate such unerased portion, it is common practice to apply a plurality of erasure impacts at the erasure position and right and left positions which are slightly offset therefrom.
If the same portion of the erasure tape is repetitively used for the plurality of erasure impacts, the following problems are encountered. In the case of lift-off erasure tapes having an adhesive surface, a small amount of ink which is stuck to a portion of the adhesive tape during a first erasure impact is transferred to the printing paper. In the case of cover-up erasure tapes, since the same portion thereof cannot be used two or more times, it is impossible to achieve complete erasure. For this reason, the erasure or correction tape is shifted a small amount upwardly or downwardly to avoid use of the same portion.
However, even if the erasure tape is controlled to be shifted the same actual amount upwardly or downwardly, the amount of shift of the erasure tape per se is changed by various factors such as the adhesive force of the erasure tape, the hardness or resiliency of the erasure tape, and the speed at which the erasure tape is peeled from printing paper. This leads to the following problems.
In erasing characters such as "I" having a large capital height, if the erasure tape is shifted upwardly or downwardly, the erasure tape is partially offset from the character and an unerased portion may be left. In contrast, in order to solve the problem, it may be considered that the amount of shift of each kind of erasure tape is reduced so that the erasure tape may completely cover the area occupied by the character. As a result, it becomes difficult to shift some kinds of erasure tape and this leads to a lowering in the efficiency of the erasure function of the apparatus.